netdev - RE: [PATCH] bpf/sockmap: fix kernel panic at __tcp_bpf

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Date:   Tue, 26 May 2020 14:10:31 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     dihu <anny.hu@...ux.alibaba.com>,
        Eric Dumazet <edumazet@...gle.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        KP Singh <kpsingh@...omium.org>,
        netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] bpf/sockmap: fix kernel panic at __tcp_bpf_recvmsg

dihu wrote:
> From 865a45747de6b68fd02a0ff128a69a5c8feb73c3 Mon Sep 17 00:00:00 2001
> From: dihu <anny.hu@...ux.alibaba.com>
> Date: Mon, 25 May 2020 17:23:16 +0800
> Subject: [PATCH] bpf/sockmap: fix kernel panic at __tcp_bpf_recvmsg
> 
> When user application calls read() with MSG_PEEK flag to read data
> of bpf sockmap socket, kernel panic happens at
> __tcp_bpf_recvmsg+0x12c/0x350. sk_msg is not removed from ingress_msg
> queue after read out under MSG_PEEK flag is set. Because it's not
> judged whether sk_msg is the last msg of ingress_msg queue, the next
> sk_msg may be the head of ingress_msg queue, whose memory address of
> sg page is invalid. So it's necessary to add check codes to prevent
> this problem.
> 
> [20759.125457] BUG: kernel NULL pointer dereference, address:
> 0000000000000008
> [20759.132118] CPU: 53 PID: 51378 Comm: envoy Tainted: G            E
> 5.4.32 #1
> [20759.140890] Hardware name: Inspur SA5212M4/YZMB-00370-109, BIOS
> 4.1.12 06/18/2017
> [20759.149734] RIP: 0010:copy_page_to_iter+0xad/0x300
> [20759.270877] __tcp_bpf_recvmsg+0x12c/0x350
> [20759.276099] tcp_bpf_recvmsg+0x113/0x370
> [20759.281137] inet_recvmsg+0x55/0xc0
> [20759.285734] __sys_recvfrom+0xc8/0x130
> [20759.290566] ? __audit_syscall_entry+0x103/0x130
> [20759.296227] ? syscall_trace_enter+0x1d2/0x2d0
> [20759.301700] ? __audit_syscall_exit+0x1e4/0x290
> [20759.307235] __x64_sys_recvfrom+0x24/0x30
> [20759.312226] do_syscall_64+0x55/0x1b0
> [20759.316852] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Signed-off-by: dihu <anny.hu@...ux.alibaba.com>
> ---
>  net/ipv4/tcp_bpf.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
> index 5a05327..c0d4624 100644
> --- a/net/ipv4/tcp_bpf.c
> +++ b/net/ipv4/tcp_bpf.c
> @@ -64,6 +64,9 @@ int __tcp_bpf_recvmsg(struct sock *sk, struct sk_psock *psock,
>    } while (i != msg_rx->sg.end);
> 
>    if (unlikely(peek)) {
> +   if (msg_rx == list_last_entry(&psock->ingress_msg,
> +       struct sk_msg, list))
> +    break;


Thanks. Change looks good but spacing is a bit off . Can we
turn those spaces into tabs? Otherwise adding fixes tag and
my ack would be great.

Fixes: 02c558b2d5d67 ("bpf: sockmap, support for msg_peek in sk_msg with redirect ingress")
Acked-by: John Fastabend <john.fastabend@...il.com>